code: def __init__(self, dbFilePath, frequency, maxLen=None):
      if os.path.exists(dbFilePath):
          raise Exception("File exists")
  
      self.__dbFilePath = dbFilePath
      self.__frequency = frequency
      self.__feed = None
      self.__maxLen = maxLen
  
file_path: pyalgotrade/testcases/dbfeed_test.py
imports: import os
  from six.moves import xrange
  from .None import common
  from .None import feed_test
  from pyalgotrade.barfeed import yahoofeed
  from pyalgotrade.barfeed import sqlitefeed
  from pyalgotrade import bar
  from pyalgotrade import marketsession
label_desc: Use image node_id 1 to create a new TemporarySQLiteFeed object  with example: obj = TemporarySQLiteFeed(dbFilePath, frequency, maxLen)